It is not clear whether Ruskin had any particular works or painters in mind here. Mengs as well as Battoni were defined as Italian by Reynolds in Discourse Fourteen of 1790 ( Reynolds, Discourses, p. 248). Léopold Robert - whose The Return of the Harvesters from the Pontine Marshes of 1830 is in the Louvre and who lived in Italy and had some influence there is mentioned at Works, 15.112.
Kugler comments:
In the exhibitions of modern productions, the traveller finds little to arrest his attention. Copies from the great work of former ages, views of the most celebrated classic landscapes, or now and then scenes illustrating the manners of the people, which the traveller carries to his home as remembrances of costume, form the far greater proportion of modern Italian productions and are rather objects of commercial speculation than indications of a vital impulse in Art. ( Kugler, ed. Eastlake, Handbook of the History of Painting, Part One, The Italian Schools, First Edition, p. 422)